An injection device in which a latching part which is connected in a rotationally fixed manner to the operating button and interacts with the injection sleeve is provided is known from WO 2013/117332 A1. When setting an amount of injection fluid to be squeezed out, the operating button is rotated in relation to the housing, and when the injection fluid is being squeezed out, is held so as to be rotationally fixed in relation to the housing and guided in the longitudinal direction of the injection device. When setting an amount of injection fluid to be squeezed out, and when the injection fluid is being squeezed out of the container, the injection sleeve is moved in the direction of the longitudinal central axis of the injection device, without being rotated in relation to the housing. On account thereof, the rotational position of the operating button in relation to the injection sleeve is modified in the case of each injection procedure.
A second latching installation of WO 2013/117332 A1 acts between a housing part and a dosing member. The dosing member rotates when setting the amount of an injection fluid to be squeezed out, and the dosing member rotates back when the amount of injection fluid to be squeezed out is being squeezed out. The latching installation has two latching arms which are disposed so as to be mutually opposite. Since the dosing member is rotatable about the longitudinal central axis by multiple rotations, each latching position is reached multiple times when setting the maximum dosage.
If and when, for example, amounts of 0.20 ml and 0.25 ml of injection fluid which are to be set for a therapy are required, then known injection devices are conceived such that dosing increments of at most 0.05 ml are settable. This means, on the one hand, that the user has to overcome a plurality of latching steps until the minimum dosage which is provided for the therapy is reached. On the other hand, the amount of injection fluid which has to be discarded during the priming procedure is comparatively sizeable in the case of a minimum fixed dosage increment of 0.05 ml, for example. Therefore, significantly smaller dosing increments would be desirable for the priming procedure. However, this leads to a significantly increased number of latching positions which have to be overcome by the user when setting the dosage.